Cambrian Stage 2
| Cambrian Stage 2 | |
|---|---|
| ~529 – ~521 Ma | |
| Chronology | |
Cambrian Graphical Timeline -540 — – -535 — – -530 — – -525 — – -520 — – -515 — – -510 — – -505 — – -500 — – -495 — – -490 — – -485 — – Major Glacial period | |
| Etymology | |
| Name formality | Informal |
| Usage information | |
| Celestial body | Earth |
| Regional usage | Global (ICS) |
| Time scale(s) used | ICS Time Scale |
| Definition | |
| Chronological unit | Age |
| Stratigraphic unit | Stage |
| Time span formality | Formal |
| Lower boundary definition | Not formally defined |
| Lower boundary definition candidates | First appearance of small shelly fauna or Archaeocyathids |
| Lower boundary GSSP candidate section(s) | None |
| Upper boundary definition | Not formally defined |
| Upper boundary definition candidates | FAD of Trilobites |
| Upper boundary GSSP candidate section(s) | None |
Stage 2 of the Cambrian is the unnamed upper stage of the Terreneuvian series. It lies atop the Fortunian and below Stage 3 of the Cambrian. It is commonly referred to as the Tommotian, after the Cambrian stratigraphy of Siberia.[2] Neither the upper nor lower boundary has yet been defined by the International Commission on Stratigraphy.[3] The preferred definitions for the lower boundary are the first appearance of the molluscs Watsonella crosbyi or Aldanella attleborensis around 529 million years ago.[4] The proposed upper boundary might be the first appearance of trilobites around 521 million years ago.[3]
Possible candidates for a GSSP include the first appearance of Watsonella crosbyi in the Zhujiaqing Formation in Yunnan, China or the Pestrotsvet Formation near the Aldan River on the Siberian Platform.[5]
References[edit]
- ^ "Chart/Time Scale". www.stratigraphy.org. International Commission on Stratigraphy.
- ^ Kouchinsky, Artem; Bengtson, Stefan; Missarzhevsky, Vladimir V.; Pelechaty, Shane; Torssander, Peter; Val'kov, Anatolij K. (24 September 2001). "Carbon isotope stratigraphy and the problem of a pre-Tommotian stage in Siberia". Geological Magazine. 138 (4): 387–396. Bibcode:2001GeoM..138..387K. doi:10.1017/S0016756801005684.
- ^ a b "GSSP List ICS". ICS. Archived from the original on 15 November 2012. Retrieved 9 November 2012.
- ^ "International Commission on Stratigraphy".
- ^ Li, Guoxiang; Zhao, Xin; Gubanov, Alexander; Zhu, Maoyan; Na, Lin (1 April 2011). "Early Cambrian Mollusc Watsonella crosbyi: A Potential GSSP Index Fossil for the Base of the Cambrian Stage 2". Acta Geologica Sinica - English Edition. 85 (2): 309–319. doi:10.1111/j.1755-6724.2011.00400.x.
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